Amber Rudd said on Saturday that investigators still do not know where the attack came from but that it “wasn’t targeted at the NHS”.

The National Cyber Security Centre (NCSC) has said it was part of a set of global cyber attacks against “thousands of organisations and individuals in dozens of countries” as it launched a major operation in response.

The Home Secretary said that patient data is secure and that no patient data has been accessed or transferred “in any way”.

At least 30 health service organisations in England and Scotland were infiltrated by the ransomware, while many others shut down servers as a precautionary measure, bringing added disruption yesterday afternoon.

Speaking to BBC’s Radio 4’s Today programme, Rudd said there “will be lessons to learn”, one of which is why certain regions were affected and others were not.

The Tory minister queried whether the breach happened because “people in certain areas are following good advice” and downloading anti-virus software.

It has been reported that 90% of NHS hospitals are still using Windows XP.

Experts have suggested that the 2001 operating system has made the NHS vulnerable to cyber-attacks.

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The message displaying on NHS computers.

Rudd agreed that Windows XP is not as secure as modern platforms and urged trusts to upgrade their software.

“Cyber-security is a huge industry and it is an area where we can all do better to protect our businesses and our personal information,” Rudd said.

“I would expect NHS trusts to learn from this and to make sure that they do upgrade.”

We're upgrading Trident but can't afford to upgrade the NHS off Windows XP; thankfully this not a state vs state cyber attack, eh, Theresa?

Despite the huge security breach, the Home Secretary maintained that the UK are global leaders in cyber security.

She said: “We do lead the world in cyber security, but it doesn’t mean that we’re not vulnerable to attacks from people that want to attack us and use the internet and cyber attacks as a vehicle for doing so but let’s look at what is actually happened over the past 24 hours.

“So far, all we have seen is patients inconvenienced, so hospitals, so doctors making changes to their daily life but the fact is that no patient data has yet been accessed and the NHS are brilliantly managing to weave through this disruption.”

Amber Rudd: "We do lead the world in cyber security." Pity the rest of the world. #today